Wave amplifying circuit



March 26, 1935.

E. PETERSON WAVE AMPLIFYING CIRCUIT Filed March 24, 1930 000 ORDER PRODUCTS lA/l/ENTOR E. PETERSON A TTORNE Y Patented Mar. 26, 1935 ED ST T-E errc I V wave- AMPLIFrING cmoorr Eugene Peterson, York ,,N. Y., assignor to I a Bell .Telephone Laboratories, Incorporated, New York, N.,Y.,acorporationoi' New York Application, March 24, 1930, Serial No. 4-38,252

' 9 Claims. '(ol. 1797-171 q g The present invention" relates "to space disof the principle of operation of the invention; and charge repeaters or amplifiers and in'particular Figs. 4 and 5 are schematic circuit diagrams of, to the operation of such apparatus to reduce or two forms of embodiment which the invention eliminate undesired frequencycomponents'in the may take, in wave amplifying systems. 5 output current. r 1 Fig. 1 shows two dynamic curves I and II, ideal l 5 An object of the invention is to secure efiicient in that they are straight rather than curvilinear amplification of applied 'waves while reducing n form. y ve, however, to illustrate h or suppressing in the output circuit the odd order p i p of Operation o the ve tione modulation products.- cathode potential or zero for this diagram is 10 The invention'is applicable to'wave repeaters shown at 0. The two tubes are biased symmetri- .10 and amplifiers for any purpose, but is particulareellywith e pect o a Va ve Eo, one tube (11)" 1 ly advantageous in-the amplification of high frebeing biased to operate about a point on its 1dy-. quency signaling waves such as are utilized in namie a a s at Vo g 8, from the yradio or carrier wave transmission systems. Genham 1ta the Ot ub to p a 15 erally in such uses it is found that the even order b ut a Point fi ts y a Characteristic by 15 products of modulation; (e. g. the double fre-' t va u Th appl d alt a v tag squency, etc.) fall outside the transmitted frena ha a p a v l a E wh ch in p a tice may quency range. Some of the odd order productsof continually y between i l mits. n modulation, however, may fall within the trans-. Under these Conditions, for all values of E eq al itt d b nd, Fo l if we id ft to and greater than e, (abscissaeithe odd order 20 amplification of two side band frequencies at D T S ates) are given by 0.5 and 60.7 kilocycles respectively, the second i f which it is seen h these products order products comprising the double frequencies from the t t are qu d DD n Si n. and the sum and differencefrequencies are 121, In p i e yn rv mo n ar y lik 121.4, 0.2 and 121.2 kilocycles, an of which are those of 3 a e en ountered, which are not 25 V remote from the transmitted band which would Straight t are 'c ss' so l be near 60 kilocycles The third orderproducts es the dynamic charac s pp a ar are 181.5, 182.1, 181.7, 181.9, 60.3 and 60. 9 kilorather a p ic o ws is usua y the casecycles, the last two of which cannot be removed especially Withlarge applied alternating grid- Voltby frequency discrimination when an appreciable egedt l POSSibIetO pp d medll- 30 side band width is used. The same general ef- 13131011 products YD P Choice of bias for the i t are t for higher odd orders of m dm two tubes.- In this case the two bias voltages will tion, that is, certain of the products will fall close generally need to be unsymmetrical With respect to or within the transmitted frequency range. to E0 instead of Symmetrical as in ig- If In accgrdance the pr esent invention symmetrical bias voltages are used. for'curveddy- 35 h b found th t't (or nm b of) namic'characteristics of the Fig. 3 type, it is found. high emgiency amplifiers a be associated in that the odd order modulation products from the manner such as to eliminate the odd orders of t tubes have Opposite bl their emphmodmation by properly choqsihg t operating tudes are not quite equal. These products can be 40 points on their characteristic curves. The two Suppressed y use of unsymmetrical biases, by space discharge devices may be "associated in Proper r io n of load imp 'apparallel with each other or in push pull relation, 'phed e e a-gesor otherwise, and are operated with their dynamic i In each of the above dlscussed W characteristics displaced a proper amount to rem tubes are duce or eliminate the odd order modulation prodphase g hence anthmetlcainy' llets pp aring in the common output circuit. i i t two t '11 are The displacement of the dynamic characteristics 283 11 s; 1 g i g Waves m is controlled by the magnitude of the negative load circuit 13 g s j f g g a gi g fig 13 made unequal m the tive grid bias voltage from battery 14 and its characteristic may correspond to curve II of Fig. A e complete understanqmg of h mVen' 3, its bias being such as to cause operationabout tion will be had from the detailed description to a i t n its dynamic characteristic. -Tube "11 follow, taken together with the attached drawing has its grid biased negatively a greater amount of which Figs. 1, 2 and 3 show curves explanatory by battery 15, and its characteristic may corre 55 In actual practice, source 12 may be anysource j of signal waves to be amplified. In the case, of a radio or carrier system, source'l2 may be'a cir-' cuit carrying side band components of a speechmodulated carrier wave, and load 13 may be an antenna or line circuit, including in either case suitable selective circuit elements or filters.

Each tube l0, 11 is, of course, indicative of any number'of tubes, similarly associated in. groups, respectively.

r .In Fig. 5, the tube -i and 11 are shown connected in pushepull f ashion The circuit is not balanced for even -order. components as inthe usualrcase .of, a push-pull amplifier, but is balanced for. odd order modulation products by use ,ofdifferent values of gridbiasvcitages 14, 15 as explained inconnection with Fig. 4. v V

. The use of separate input and separate output couplingsfor the ,tubeslO and 11 also permits of varyingthe input A. C. voltage and load impedance, on the two tubes to assist in suppressing the ,odd order modulation products; if necessary.

The circuits and graphs are to be taken as illustrative and-not as limiting the invention, since a variety of formsof embodiment are possible.

What is claimed is; h r j l 1. In a wave amplifying circuit a pair of threeelement space discharge devices having a common input circuit and a common output circuit, the grids. of said devices having different respective negative grid bias voltages substantially symmetrical with respect to the dynamic cut-off point.

2. In a' wave amplifying circuit two three-element vacuum tubes having a common input and a common output circuit'the grid of one of said tubes being more negatively biasedthan the dynamic cut-off point, and the grid of theother tube being less negatively; biased than the dynamic cut-off pointby an amount sufficient to neutralize in the common output circuit the odd order modulation components from the first tube. 7 3. In a wave repeating circuit comprising two space discharge devices each having a cathode, an anode and a grid or'impedance control element, a

source of waves applied to the input circuits of both devices, a load circuit, coupled to the output circuits of both devices in common, and means to bias the grids of said devices in the vicinity of the dynamic cut-,off point by respectively different amounts sufiicient to cause one device to neutralize the production. by theother device in the load space discharge devices each having a cathode, an anode and a grid or impedance control element, a source of waves applied to the input circuits of both devices, a load circuit coupled to the output circuits of both devices in common, and means to bias one grid more negatively than the dynamic cut-off and the other grid negatively by a different amount, such as to oppose the production in the load circuitv of odd order modulation components arising from the first device.

5. The method of suppressingthird order and higher oddorder modulation products in a wave amplifier comprising amplifying the waves by a pair ofsimilar space discharge devices, and oppositely biasing the control electrodes of said devices with respect to theirdynamic cut-ofi voltages by an amount sufficient to make said odd order components occurring in the output circuits to have substantially the same amplitude but I opposite phases.

6. In a wave repeating circuit two space discharge devices eachhaving a cathode, an anode and a grid or controlelement, a common input circuit for both devices including a source of waves to be repeated, means for normally biasing the grid of one device more negatively than the dynamic cut-off point, means for biasing the grid of the other tube less negatively than the dynamic cut-ofi point, the respective values of grid bias on the two devices beingadjusted to .cause the odd order modulation products in the output of onedevice resulting from the application of saidwaves to its input circuit to oppose the oddorder modulation products of said waves in the output of the other device.

'7. The method of reducing third harmonics in the common load circuit of a. pair of triodes consistin gin biasing the control electrode of one of the triodes to a greater extent than the control electrode of the other triode, and biasing the control electrode of the latter in such a manner that third harmonics produced in said load circuit by of a pair of plural-electrode tubes having grids or control elements which consists in connecting a pair of said tubes in parallel, biasing the control element of one of the tubes to a greater extent than the controlelement of theother tube, the bias voltages on the control elements of the respective tubes being of such values as to tend to cause production in theiload circuit by the respective tubes of undesired odd order modulation products of'respectively opposite phase whereby theamount of said undesired odd order modulation products present irrsaid load circuit is the difference between the amounts of said products generated in the two tubes.

' 'EUGENE PETERSON. 

